regulator: palmas: Fix "enable_reg" to point to the correct reg for SMPS10

regulator_enable_regmap() uses enable_reg to enable the regulator.
But enable_reg for smps10 points to SMPS10_STATUS which is a
read-only register. Fixed the same by having enable_reg
set to SMPS10_CTRL.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@vger.kernel.org